What is suitable Target CPA in AdWords?

[TisTis]

I started a Google AdWords campaign for one of my games.
And now I try to find a suitable value for the target CPA.
The help doc of AdWords is not that clear about this matter.

Please, could you give me some advice?

 

[Forsbit]

CPA depends on many factors, like CTR and install conversions, etc. Usually you start with high traget CPA and after you get some installs, adjust it to come up with a value that gets you downloads at minimum cost